Probably. But Obama is talking about repealing "dont ask dont tell" so you would be ok as a homosexual at some point in the near future
I have no idea how Obama would deal with this though.
If you tell any of your superiors that you are gay, the shit will start hitting the fan, and yes you will probably be discharged. You will be investigated, if they find out you're straight and doing it just to get discharged, you will land yourself in the brig for falsifying official documents, dereliction of duty, disobedience of a superior commisionned officer.
so you better be ready to prove it, but if you're getting a sex change, i guess thats proof enough. so uh. good luck buddy, or uh.. whatever you think you are =)